; tend to values like pi/8
; pi/8  = 1/(1*3)+1/(5*7)+1/(9*11)+...
; a = 1, 5, 9 ...
; b = a + 2

(define (pi-sum a b)
    (if (> a b)
    0
    (+ (/ 1.0 (* a (+ a 2)))
       (pi-sum (+ a 4) b))))

; (trace pi-sum)
(pi-sum 1 8)



